:D means a defined value. So it's when you have an instance. :U is
undefined so it's when you call kv as a classethod.
Pair.kv would be :U.
(A => "b").kv would be :D
On Fri, 14 Sep 2018, 11:22 Todd Chester, <toddandma...@zoho.com> wrote:
> Hi All,
>
> I adore the "kv" method:
>
> $ p6 'for "abc\n23\n4.56".lines.kv -> $i, $j { say "$i $j" };'
> 0 abc
> 1 23
> 2 4.56
>
> So, I decided to go and look at:
> https://docs.perl6.org/routine/kv
>
> multi method kv(Any:U: -->List)
> multi method kv(Any:D: -->List)
>
>
> Okay, here is what I see:
>
> "method" is .foo style of a routine
>
> "Any:U:" and "Any:D:" are what goes in front of .foo
> and it can be of type "Any".
>
> https://docs.perl6.org/type/Any
>
> ":D" mean constrained, meaning it much have something
>
> What is ":U"?
>
> Whatever ":U", how can it be both?
>
> The second ":" is the delimiter for what goes in front of the .foo,
> meaning it has finished its declaration of what that in front is.
> Kind of like a comma.
>
> "-->List" mean something is returned of type "List"
> https://docs.perl6.org/type/List
>
> 0 abc
> 1 23
> 2 4.56
>
>
> How have I done so far?
>
>
> And is there a list somewhere of the meanings of ":U" and ":D"
> and such so the next time I see one that I do not recognize,
> I can look it up?
>
> Many thanks,
> -T
>
